Coating apparatus for making pressure-sensitive tape



July 28, 1953 COATING APPARATUS FOR MAKING PRESSURE-SENSITIVE TAPE Filed July 24, 1948 @f af; g @E Patented July 28,

COATING APPARATUS FOR MAKING PRESSURE-SENSITIVE TAPE y Milton H. Kemp, Michigan City,v Incl., assignnor to The Scholl Mfg. Co., Inc., Chicago, lll., a

corporationzof New York Application July 24, 1948, Serial No. 40,498

The present invention relates to a method of making pressure-sensitive tape, and, more particularly, vto a method of making paper-backed pressure-sensitive tape suitable for use as a masking tape and to apparatus for makingvthe same.

My novel tape andthe method of making the same are more fully set forth, described and claimed in my copending application entitled Pressure-Sensitive Adhesive Tape and Method of Making The Same, filed March 17, 1949, Serial No. 81,954, now U. S. Patent No. 2,557,227.

In accordance with the present invention, a backing member of fibrous material, such as a sheet-like paper web, is coated with a pressuresensitive adhesive composition by means of a simple, easily conducted, continuous process. The method of the present invention contemplates the pre-wetting of the fibrous web with a solvent for the adhesive composition later applied thereto. The pre-wetted web is then coated with a pressure-sensitive adhesive to apply a continuous, uniform layer of adhesive upon one sur face of the web. Following the application of the adhesive material, the coated web is dried land formed into a roll for further processing or for sale as a completed article of manufacture.

The fibrous web to which the adhesive is applied may suitably be a continuous paper web, which has preferably been well sized or impregnated with a synthetic rubber composition or similar material. If desired, that surface of the web opposing the surface to which the solvent and adhesive are applied may be coated with a synthetic resin composition such as, for example, a nitrocellulose or ethyl cellulose coating composition.

, I have found that, in the coating of adhesive material to a fibrous backing surface, voids, and gas blisters or air bubbles may be formed, during the drying operation, between the adhesive and the surface to which it is applied. The formation of these bubbles or voids prevents the close adherence and bonding o-f the adhesive to the surface with the result that, in stripping the tape from a roll of the tape or from a surface to which the tape has been applied, the backing surface may become separated from the adhesive. This is referred toas delamination. Delamination is preventedbythe method of the present invention, `in which a solvent for the adhesive material is applied to the surface prior to the application of thepressure sensitive adhesive to that surface.

\The apparatus of the present invention pro- 'vides novel means for applying the solvent to the surface ofthe backing material and also provides improved means forthe application of the adhesive materialN to the wetted backing surface.

The apparatus for applying solvent to the webcomprises generally a reservoir mounted adjacent the web and wick-like means extending from the reservoir into contact with the web so that the web is evenly wetted along its entire surface.

The improved means for applying adhesive to the web following the wetting of the sheet with solvent comprises a pair of cooperating elements extending on either side of the web to define a restricted nip. Novel means are provided for obtaining relative movement between these cooperating elements, both in the direction of travel of the web and toward each other. The adhesive material, preferably in the form of a plastic stock mass, is applied to thepre-wetted web as it passes through the nip provided between these cooperat-` ing elements. Thus, the present invention provides a method whereby an improved pressure sensitive tape may be obtained as well as'apparatus for the preparation of such tape. The pre-wetting step of the method hereinbefore described prevents the formation of bubbles, blisters Iand voids during drying between the adhesive material and the backing surface, while the improved apparatus of the present invention provides means whereby the backing surfacel may be readily pre-wet and the adhesive material may be applied to the prewetted surface without the possibility of forming voidsor bubbles.

` It is, therefore, an important object of the present invention to provide a method for the preparation of pressure-sensitive tape wherebyV a closely adherent coating of adhesive may be applied to a backing surface without the formation of bubbles or voids between the adhesive and the surface.

It is another object of the present invention to provide a method for the preparation of pressure-sensitive adhesive tape in which a fibrous backing surface is wetted with solvent prior to theapplication of the adhesive coating to the backing surface to prevent the formation during drying of voids, blisters, and bubbles between the adhesive and the backing surface.

It is a further important object of the present invention to provide apparatus for the preparation of vpressure-sensitive adhesive tape including means for applying solvent to the surface of a continuous fibrous web in combination with means for applying adhesive to the pre-wetted web surface. Y

It is a, yet further important object of the present invention to provide apparatus for the application of solvent to a sheet-like web of fibrous material, said apparatus including a reservoir adjacent the web of iibrous material and means extending from the reservoir into contact with the web of brous material, to wet the surface of the web with solvent.

It is a yet 'further important object of the present invention to provide means for the application of said adhesive material to a sheet-like web'- of fibrous material, said meansfineluclinga-pair: of cooperating elements extending on either-side@ of said web and defining a n ip therebetween, said elements being capable of relative movement to vary the size of the nip.

Many other objects and advantages of the invention will become apparent Afrom the followe ing description and the accompanying drawings, in which:

Figure 1 is a side elevational view, with parts broken away; of Ya coating apparatus'of the pres` entinvention illustrating the operation ofthe method of the present invention;

Figure 2 k-isV a fragmentarynplan, elevational view ofgaportion of the apparatus oiFigure l;

Figure 3 is a view taken along the plane III-III of Figure l;

Figure V4 is a cross-sectional view taken along the plane IV--IV of Figure 2 Figure 5 isk a cross-sectional view taken along the plane V-Vof Figure 1 and Figure 6 is a cross-sectional View taken along the plane VIA-VI of Figure 1.

As shown on the drawings:

The reference numeral i0 refers generally to a supporting framework forvsupporting the coating portion of/,the apparatus of the present invention. The frame I0- comprises a pair of spaced, horizontal, parallel members II-and I2, the member I2v being spaced from the member II by` means of `spaced vertical uprights I3 and I4.; Two such rectangular frameworks, defined by. the members II-I4, inclusive, are provided inspaced relation as shownin Figure 2 to define a generally box-like supporting structure. A n elbow extension I6-is provided for each'of the members I2;v the members I6 extending vertically above and horizontally beyond the members I2. AA second support spaced beneath the extensions i'is provided by members I'I-and I8 secured `to the members I3 and II, respectively, and joined at their free ends. Membersr I1 and ISserveto support a woundroll `of fibrous web materi-alZZ:

The web 22 islapped about a roll- 23 supported at eitherend vin, bearing blocks v2'I movable within brackets v24'seclirel to the uprights I3`ofjthe frame I Il.' The position of the roll 23 'may' be varied towardv or away from uprights I3" by means of jscrews 2,6to effect movement of the mounting blocks 2T. Roll 23, in conjunction with the` usual braking system on the supply roll 20, thusserves to maintain the web 22 undertension as it passes from the supply roll2jthrough the entireapparatus. Web 22fis next passedabout a guide roll28 journaled in the support-mem bers I6 and supported therebetween as best shown inFi'gure'Z, From the guide roll y28 the web 22 is passed over a second guide roll A29'which is likewise journaled between the members I6:-

Between the guide rolls 23-and 29 the upper surface of the web ispre-wet with a lsuitable vliquid -by means of apparatusindicatedegenerally in Figure 1 by the reference numeralh30 and illustrated in. greater-detail inr FigureA.; The apparatus 30 comprises a cylindrical tank or reservoir 3I extending between and supported by the members I6. The supporting structure for the tank 3l comprises vertical, spaced, parallel members 32 mounted on the facing surfaces of the members I6 and extending upwardly beyond the connes thereof: The upper ends of; the members 32 are connected by means of horizontal plates 33 secured to the ends of the tank 3I to support the tank in position above the web 22 passing between the rolls 28 and 29. A pair of bearinggy blocks 34 are mounted between members 32 and are journaled therein for adjustable vertical movement-by .means of screws 35.

Theblocks 34; thus movably mounted on the members I6; support a generally rectangular plate'or lbladeit.positioned directly beneath the tankv 3l. A relatively short length of rod 3l is secured, as by welding to each end of plate 36 to serve as stub shafts for the plate. The rods 37 are. .journaled in theblocks 34; asin sleeves, and are capable ci -swivelling movement inthe blocks.. Means, suchas set screws Slextending into the blocks-.zandvthrough sleeves l38.,into contactwith shafts 3'1, are provided zfor retain-- ing the stub shaftsSl'in adjusted position. O ne edge of plate 35fextends radially into aptubel through an. elongated aperture 41a, the,- entire length of the-rear edge of the platel extend-v ing` through the tube 4l .to abutthe` interiorsurv face` of the tube.

Aieltrl, having a width substantiailypthat,of the plate. islapped about the framework formed.l by the vtube ii and the plate sercured,v as by sewing, toprovide. a feltacorered,

absorbent member extending. completely across thesnrface of the web. 22. The felt tgis in 'ith theupper surface of the web; '.iand Lto engagement therewith asat ,t3 i theweb passing between the rolls 8 'and milder tension. An eiongated. slitte' extends.acrossthe-entire upper length' oiftank 3l toprov-ide means for, ill-ling and emptying vthe tank. A strip. of felt-Eef width equalY to that of i the felt: isinsertedthrougb .the slitl into a: body oiliquidA 35 contained within the tank 3 i. An elongated piate. i'extending across theelengthoi the. tank 3i is adjustablyl attached. to the tank. bynieansof capl screwsl. The amount .oisliquid absorbed-by the felt=iizand passingtherethrough vby .capillaryr` action :tothe feltfcoyering i2 may be determinedrby the set--v ting-of .the .cap screws 48: .forcing the. plate .43 intorcontact with-the strip of ,felt 45. lheld against the. outer surface. of theftank 3i. rIhus,-means are provided for regulating the amount of liquid 48 passedthrough the felt. l'nto .the :felt142 in,v Contact withzthe web 22a-eat Following thapassa'e. o. the.l web.' over the roller 2Q; the lliquid'l iettedmwieb passes .oyerz-a stationary-spreader '4Q secu-red. to-.Cplosing faces .ofthe members roland extending` therebetween. A'second sprreaderbar supported-by thefmembers .5 in closely spass-i relatontcthe spreader bar to. defineI a restrict-ed nip-therebetween.. 'Ihe spreader bar ertedby means-of-- a pairV of brackets 5i secu d to -the members 6 and extendingrthereabove.V` bracket .5l-supports pair of spaced,- up ht guide.. y members. .52; for receiving-f bearingo blocks sa.:

A; horizontal :member joins thei upper yex.- tremitiesof. eachupair of,;upifights. 52,2 as -sh'own in,Figures.1 and;. 3,.; A fscrew... 5dr: rotatably Secured.; tQf,-'the. upper surface. of.l each; block; 53

and is threaded in the member 54 to provide means for moving the block 53 while guided between the members 52. A shaft 58 is journaled in each of the blocks 53 and extends therebetween for vertical movement therewith. A bracket arm 59 is secured to each extremity of the shaft 58 for rotation therewith, each of the bracket arms abutting the inside surfaces of the blocks 53. The bracket arms 59 carry at their lower portions the guiding bar 50 for contacting the upper surface of the web 22. The members 52 carry inwardly projecting ears 60 adjacent the side surfaces of the arms 59. The ears 50 are apertured to threadedly receive set screws 5| which extend through the ears 60 into contact with one edge of the depending arms 59. The arms 59 may be moved by means of the set screws 6l to determine the size of the nip aperture defined by the guiding bars 49 and 50. The tension placed upon the web 22 passing through the nip thus defined is regulated by the braking system on the supply roll 20. The set screws 5B determine the vertically adjusted position of the blocks 53 guided by the members 52, and therefore in conjunction with the set screws 6i, determine the gap at the nip.

An adhesive mass 52 is positioned at the nip defined by the guide bars 49 and 50 to be spread upon the pre-wetted surface of the web 22. Thus, the web 22 issuing from the nip carries upon its upper surface an adhesive mass evenly spread thereon by the cooperating guide bars 49 and 50.

Following the application of the adhesive mass, the web 22 is passed through a drying chamber or oven S3 which is supported by means of a supporting frame 64 at a proper height to receive the web 22 supported by a plurality of rollers 66 mounted within the drying chamber 53. The adhesive mass when applied to the web 22 is dried to a semi-tacky condition within the drying chamber 63 so that a completed pressuresensitive tape in the form of a continuous web 6l issues from the drying chamber 63. The tape web 6l is wound about a driven roll 68 supported by a bracket 69 mounted on the supporting structure 0.. Roll 68 is driven by means of belt l0 .connected to a suitable source of power to pull the paper web through the complete coating and drying apparatus, the web being maintained under tension at all times during the manufacturing operation.

In Figure 5, the finished tape El, following the dryingA operation, comprises the sized web 22 having a coating of synthetic organic film 12 applied to one surface and the layer 62 of tacky, pressure-sensitive adhesive applied to the opposite web surface. The lm backing 12 is generally desirable, although not necessary to the practice of the method of the present invention.

It should be understood that Ythe method of the present invention may be employed to prepare pressure-sensitive tape employing any type of flexible backing material. Although I prefer to employ a paper backing, particularly in the manufacture of masking type tape, the apparatus and method herein described may be employed to prepare tape having a felted fibrous or paper fabric backing, or other suitable flexible backing material. In the use of a paper backing, it is desirable to employ a web of well sized paper stock, the web preferably being impregnated with a synthetic rubber composition. Such papers are preferred because of their high tearingstrength, flexibility and resistance to penetration bylacquersolvents.

.In some applications, it has been found to be desirable to employ a paper or other fibrous backing material having one surface coatedwith av synthetic organic film 12, such as nitro cellulose, ethyl cellulose, or othersynthetio resin films.

Component: Parts by weight Vistanex B 1 00 500 Piccolyte S p 350 Mineral oil 200 Naphtha 2000 Vistanex is a trade name employed to identify isobutylene type polymers made, for example, according to U. S. Patent No. 2,051,840. Piccolyte is a trade name of a hydrogenated terpene polymer, such as polymerized betapinene, prepared as generally set forth in U; S. Patent No. 2,249,112..

The liquid employed to pre-wet the web 22 as by means of the apparatus 30 is preferably an organic solvent such as toluol, an aliphatic naphtha such as textile spirits having a boiling range of from to 201 F., or a commercial solvent sold under the trade name Ennjay I which is a petroleum aromatic solvent having a boiling range from 209 to 242 C. I have found that the application of about 0.022 pound of solvent per square yard of web, or less, is sufficient to give a very slight wetting of the web with the solvent. Undesirable voids, blisters and air bubbles during drying in the oven, are thereby eliminated. The function of the solvent and the purpose of the pre-wetting step prior to the application of the adhesive composition to the web have been described above and result in the elimination of air bubbles, blisters or voids, during the drying step, between the surface of the web 22 and the adhesive mass applied to that surface. It should be understood that the solvent has novmutual dissolving action upon the web and the adhesive and that the improved ytape is obtainedby the elimination of voids or air bubbles between the adhesive and the web. The resulting smooth coating of adhesive applied to the web surface adheres very tenaciously to thc web and will not become delaminated during the removal of the tape from a surface to which it has been applied.

The apparatus illustrated in the drawings is particularly adapted to the pre-wetting of the webprior to the application of the adhesive and vmakes possible the continuous production of the improved type of tape herein provided. The provision of thetank in position above the surface ofthe webb to be `wetted and the employment of felt-type spreading means for introducing the solvent in controlled amounts onto the surface of the web results in the uniform application of solvent to pre-wet the tape prior to the application of adhesive. The use of this prewetting apparatus, and particularly the use of theapparatus inA 'combination with the "improved means herein provided-forapplyingathe adhesive in controlled; variableamountsrtoithexweb surface, makes possible-'the operationfoft -the'method at various web speeds andithe application of solvent to the Webfin amountaccordinggto lthe character of the backing Web :and to ther' particular adhesive employed.A The means 1". for spreading the tape 'insuresA the eicientf automatic control ofthe amount-ofv `adhesix'ze introduced onto thev pre-wetted Web-and the thick'- ness of the normally tracky adhesivellayer in the iinisned tape.; TheA apparatus of:Y therpresent invention: thus lprovides means for the controlled production of .pressureLsensiti've tsueeir'raemanL ner lnot hereinbeforerpossibles Itwillj ofA course; be understood-that `various details fof f construction may #be varied through a Wide-frange Withoutfdeparting--from-the prins ciples of this invention, and it is, therefore, not the purpose to limit the patent granted'hereon otherwisethan necessitated by the scope of the appended claims.

I claim as my invention:

1.v In apparatus for the production of pressuresensitive tape including-coating meansfforfapplying; an .Y adhesive toaf brous web..- and drying meanse for drying.; Saidfiadhesivef-,onsaid. web, means for applying; av: liquids; to .-saidv Webf im:- mediately Aahead of-,saidv coating means including a; reservoir rpositioned adjacent said webran. absorbent wick extending from said reservoiininto Contact withthat web surface :'tof.be'-later coated with ladhesive :immediately aheadof said-coating meansgf a supporting frameworklrigidii-ying that p ortionio ,the :wick cont-acting ,said .web :and inoludingga 4rigid bladezheld against rotation enclosed Yby-' 1sair.l wickfandfurging -the .wick into line contact-with the web .to deflect said` web ,from-its normal .plane o f 'travels therebyytensioningathe sameand adjustable means carrying .-saidzframework andfloadinggthe .same towardI said web ,to vary the==tensionupon said. webatits -lineoi contact Withwsaidzwick.

A'Ycoatingnpparatus comprisingfspaced supiportsfiorn norma-.ily supporting a: plane length of; tensioned fibrous .:web therebetween,.-..spaced support tmeans: alongside each' ':=lateral; edge. of saidweb, a: rigidv kvtensioning 1 blade fheldagainst rotation carriedfby-said support mea-ns and. exs tending transverselyacross said Webvin aiplane inclined with respect toithefplane ofY said web, ais/divent-y reservoir,l positioned adjacent` saidzweb, Wicksmeansi substantially; enclosing said blade means being adapted-for edge contact-while; sup-.- ported by; said :blade with one surfacevof said web vbetween said spaced- Vsupporta:,meansl f for compressingsaid Wick between Ysaid web and said bladefbyfadjusting Vsaid blade-andathe fwick car,- riedl therebyinf a-.1plane normal tozthatl 10i-,said web, and means for adjusting the inclinationfof said :blade: and saidf.-.Wick.-:relative =to :,said iweb, said :r last Atwo :.mentioned; meansf being adapted to .':varyg-thef tensionaexerte'd-:upon said=web :by said .zbladeicwi-th the. .wick-serving gto coat asaid web surface; with a :solvent` from said i-reservoir.

3. Apparatus-:aas ,-sclaime'dxin E iclaim: .1 .wherein said; adjustable.;`A meansv comprise inist-means@ for compressingsaid Wick between; said web and said blade by adjusting said 'blade andwthewick-carriedthereby in a plane normal 'tothatlof said web and second means for adjusting the inclinationof Vsaid'blade and said wick relative-to said web;

4. Apparatus as claimed inV claim 3` wherein the rigid blade is swivelly mounted onfblocks insaid framework`- and said adjustable means comprise rst means engagingsaidblocks' and saidrframeworkior Ycompressing said blade-by adjusting said blade and the wiclicarried'thereby in a plane normal to thatof saidaveb and seo-v ond means for adjusting the inclination of said blade and said wick relative to said web, said second means being mounted on said blocks.-

5. A coating apparatus comprising spaced guide rolls for normally supporting a v plane length of travelling horizontal brous web therebetween, spaced support' frames alongside' each lateral edge of said web and rotatably'mounting said 'guide rolls, blocks mounted on said frames between said rolls, a rigid generally rectangular plate lheld against rotation and swivelly carried by said blocks and extending across said web in a plane inclined with respect to theplane` of the web, a solvent tanl; positioned above and adjacent said web, wick felt substantially enc1ossaid plate and extending upwardly andl into said solvent tank, said wick being adapted for edge contact while supported by saidrlplateiwith the top surface of said web between said spaced relis, first mounting members engaging said frames and said blocks for compressing said wick between said web and said lplatev by adljusting said plate and the wick' carried l"thereby in a plane normal to that of said web, and sec-` ond mounting' members carried by said blocks and coasting with-said plate to selectively'per-y mit and prevent swivel movement 'of said plate for adjusting the inclination of said plate and said wick relative to said web, said first andseoond mounting members ybeing adapted to vary the tension exerted upon said Webby said plate with the-wick serving to coat -saidf-Websurfaoe with a Solvent from said tank.v

MELTON H'. KEMP;

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